RELATED APPLICATIONS
[0001] Reference is hereby made to commonly assigned and copending U.S. patent application
METHOD AND SYSTEM FOR SOUND EXPANSION, Serial
No. 08/858,594 [Attorney Docket No. 49617-P021
US-966319], filed concurrently herewith, and copending U. S. patent application STEREO ENHANCEMENT
SYSTEM INCLUDING SOUND LOCALIZATION SYSTEM, Serial
No. 08/511,788, filed August 7, 1995.
TECHNICAL FIELD OF THE INVENTION
[0002] This invention relates to a sound enhancing system and more particularly to a system
and method for providing full sound image coverage when a listener has less than the
full compliment of speakers required to hear all of the available sound.
BACKGROUND OF THE INVENTION
[0003] There are sound systems available which provide a listener with a full sound experience
such that the reproduced sound appears to come to the listener as though it were being
played "live" in the presence of the listener.
[0004] The DOLBY (a trademark of Dolby Labs) surround systems are typical of such systems
where a listener can enjoy a full range of sound spread out in a three dimensional
pattern around the listener. One major drawback to such systems is that they require
more than the traditional two (left and right) speakers. Typically, these systems
require at least three (the third being a center speaker for speech and other "centered"
sounds) and usually also require two rear speakers. For maximum enjoyment at least
one sub-woofer is also required so that the listener can hear and perhaps even feel
sounds in the range from 100 Hz and below. In addition, most existing surround systems
provide the same sound to both rear speakers. An example of a system in which the
rear speakers have the same sound signals is Dolby ProLogic.
[0005] New systems are coming on the market whereby an improvement has been made in that
the rear speakers actually receive different sound signals thereby creating a left
and right effect to the rear of the listener. An example of a prior art system in
which the rear speakers have different sound signals is Dolby Digital (AC3).
[0006] The above-described systems assume a very import parameter that simply is not true
in most situations. The assumption is that listeners of the sound system will have
the five (or more) speakers necessary to take advantage of the full range of the sound
systems. Most people simply can not afford to, or choose not to, install in their
listening area the number (and quality) of speakers necessary for enjoyment of these
full sound systems. Also, most people have more than one location from which they
wish to listen to music, the TV, etc., and the need for five (or more) speakers limits
their listening options considerably.
[0007] Furthermore, computer enthusiasts are precluded from taking advantage of the surround
sound systems described above where use of more than two speakers is awkward.
[0008] Accordingly, a need exists in the art for a system which can accept the five sound
signal inputs (left front, right front, center front, left rear and right rear) for
a surround sound system and to convert those signal inputs for presentation to left
and right front speakers while still maintaining the full sound experience for the
listener.
[0009] A further need exists in the art for such a system in which the sound signal inputs
for the rear speakers can be either the same or different for each speaker.
[0010] US 4,159,397 discloses a system for accepting a set of n input signals for presentation to x speakers,
where x is any number, the system comprising means for expanding in pairs certain
of the signals for presentation to the x speakers, means for expanding in pairs others
of the input signals for presentation to the x speakers and means when x is less than
n for summing the expanded signal pairs for presentation to the x speakers.
SUMMARY OF THE INVENTION
[0011] These and other objects and features of our invention are achieved by a system as
claimed hereinafter, and whereby in a first embodiment the five sound signal inputs
from a full sound system (left front, right front, center, left rear, right rear)
are converted to sound signals for presentation to left and right front speakers while
preserving for the listener the perception that the sound is coming from fully around
the listener. The system is designed such that speech and other front center speaker
sounds still are perceived as coming from the center front while sounds which would
be directed to the left and right rear speakers appear to the listener as coming from
the same area as the "missing" rear speakers.
[0012] In an alternate embodiment, we have designed a system which will accept five sound
signal inputs where the rear sound signals can be identical for both rear speakers
or can be different for the two rear speakers.
[0013] In a second alternate embodiment, we have designed a system which will accept the
five sound signal inputs and expand the sound from the front and rear pairs of speakers
so that the sound appears to a listener to be coming from locations beyond the physical
boundaries of the five speakers.
[0014] The embodiments discussed above take advantage of sound expansion techniques known
in the art and on techniques based on copending patent application entitled METHOD
AND SYSTEM FOR SOUND EXPANSION. The prior art techniques for sound positioning are
disclosed in
U.S. Patents 5,105,462 and
5,208,860 issued to Lowe et al. on April 14, 1992, and May 4, 1993, respectively, which are
illustrations of systems for positioning sound images at any desired location around
a listener. The Lowe patents take a monaural sound image input and position that sound
image at a selected location. The systems discussed in the above-identified patents
is herein referred to as the Q1 system.
[0015] Techniques for stereo expansion are disclosed in
U.S. Patent 5,440,638 issued to Lowe et al. on August 8, 1995. The system discussed in the above identified
patent is herein referred to as the QX system.
[0016] Thus, it is one technical advantage of our system and method that a five input sound
signal system can be processed in a manner that will allow the sound to be expanded
so that it will appear to a listener as though it emanates from five speakers while
only two speakers are used.
[0017] It is a further technical advantage that the system will operate properly in situations
where the sound signal inputs which would be directed to the two rear speakers have
the same content and when they have different content.
[0018] It is a still further technical advantage of our system that it can be used in situations
where the listener has five speakers placed around a listening area or when the listener
has only two speakers and the sound input for the rear speakers is monaural or stereo.
[0019] The foregoing has outlined rather broadly the features and technical advantages of
the present invention in order that the detailed description of the invention that
follows may be better understood. Additional features and advantages of the invention
will be described hereinafter which form the subject of the claims of the invention.
It should be appreciated by those skilled in the art that the conception and the specific
embodiment disclosed may be readily utilized as a basis for modifying or designing
other structures for carrying out the same purposes of the present invention. It should
also be realized by those skilled in the art that such equivalent constructions do
not depart from the scope of the invention as set forth in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] For a more complete understanding of the present invention, and the advantages thereof,
reference is now made to the following descriptions taken in conjunction with the
accompanying drawings, in which:
FIGURES 1A, 1B and 1C show embodiments of our invention for operation where the rear
speaker inputs are different, together with a pictorial of the speaker placement and
a diagram of the enhanced sound image as perceived by a listener;
FIGURES 2A, 2B and 2C show other embodiments of our invention where the rear speaker
inputs are the same, together with a pictorial of the speaker placement and a diagram
of the enhanced sound image as perceived by a listener;
FIGURES 3A, 3B and 3C show still other embodiments of our invention for providing
enhanced sound imaging for use in situations where the listener has five speakers
and the sound signals for the rear speaker are monaural, together with a pictorial
of the speaker placement and a diagram of the enhanced sound images as perceived by
a listener;
FIGURES 4A, 4B and 4C show still other embodiments of our invention for providing
enhanced sound imaging for use in situations where the listener has five speakers
and the sound signals for the rear speaker are stereo, together with a pictorial of
the speaker placement and a diagram of the enhanced sound images as perceived by a
listener; and
FIGURE 5 shows a monaural to stereo conversion circuit, also referred to as a 123D circuit;
FIGURE 6 shows an omni to stereo conversion circuit, also referred to as an OMNI23D circuit;
FIGURE 7 shows the prior art Q1 circuit for producing a left virtual image; and
FIGURES 8A and 8B show different versions of the QX circuit.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Before beginning a detailed discussion of the operation of the various embodiments
of our invention it should be noted that the detailed operation of the 1
23D, OMNI
23D, Q1, single and dual QX circuits, various embodiments of which are shown in FIGURES
5, 6, 7, 8A and 8B, respectively, together with sound enhancement diagrams, can be
found in the above-discussed copending patent application and patents. These details
will not be repeated herein.
[0022] Turning now to FIGURE 1A, there is shown circuit 10 which is designed to accept five
sound signal inputs, 11, 12, 13, 14 and 15 and to combine the rear sound signals with
the front sound images to provide an enhanced full dimensional sound output image
to listener 100 via only left speaker 16 and right speaker 17. To date, prior art
systems have only been able to combine five input signals to produce the left 16,
right 17 and center 110 sound images as shown in FIGURE 1B. FIGURE 1C shows sound
images 120, 121 and 122 perceived by listener 100 when the sound input signals are
processed by circuit 10.
[0023] As shown in FIGURE 1A left and right front inputs 11 and 12 are provided as respective
inputs to QX filter 101. This QX filter can be either that shown in FIGURE 8A or in
FIGURE 8B. The left and right outputs of filter 101 then form one input to each of
summers 104 and 106, the other input to each of these summers is the output of attenuator
102. Attenuator 102 provides an attenuation of center input 13 in the range of -6dB
to zero with -3dB in a preferred embodiment. The output of summers 104 and 106 are
input to the input of summers 105 and 107, respectively. The other input to each of
summers 105 and 107 come from the left and right outputs of expansion circuit 103.
Note, that in situations where a center speaker is available, the input for the center
speaker would be presented to the center speaker without attenuation and without being
summed with the other speaker signals.
[0024] Expansion circuit 103 receives rear left and right stereo sound signal inputs 14
and 15 and converts that input to an expanded sound image by using a pair of the circuits
shown in FIGURE 7 or preferably the circuit shown in FIGURE 6.
[0025] In another embodiment, expansion circuit 103 may be comprised of either of the circuits
shown in FIGURES 8A and 8B if attenuators 1615 and 1619 effectuate an attenuation
in the range of approximately -20 dB to approximately -80dB.
[0026] The output of summers 105 and 107 form the inputs to speakers 16 and 17 to create
the sound enhanced image shown in FIGURE 1C.
[0027] Turning now to FIGURE 2A there is shown circuit 20 which is designed to accept four
different sound signal inputs, 11, 12, 13, and 21, where input 21 is a monaural signal
for presentation to the rear two speakers of a five-speaker system. Circuit 20 combines
the rear sound signal inputs with the front sound signal inputs to provide an enhanced
full dimensional sound output image to listener 100 via left speaker 16 and right
speaker 17. To date, prior art systems have only been able to combine five input signals
to produce the left 16, right 17, and center 210 sound images as shown in FIGURE 2B.
FIGURE 2C shows sound images 220, 221 and 222 perceived by listener 100 when the sound
input signals are processed by circuit 20.
[0028] As shown in FIGURE 2A left and right front inputs 11 and 12 are provided as respective
inputs to QX filter 101. As discussed above, this QX filter can be either that shown
in FIGURE 8A or in FIGURE 8B. The left and right outputs of filter 101 then form one
input to each of summers 104 and 106, the other input to each of these summers comes
from a 3dB attenuation, via box 102, of center input 13. The output of summers 104
and 106 are input to summers 105 and 107, respectively. The other inputs to summers
105 and 107 come from the left and right outputs of expansion circuit 201.
[0029] Expansion circuit 201 receives a monaural sound signal 21, which can come from various
sources such as, by way of example, from the rear "surround" outputs of the above-mentioned
Dolby ProLogic system. Circuit 201 operates to convert that monaural input to an expanded
sound image by using the circuit shown in FIGURE 5 or preferably the circuit shown
in FIGURE 6.
[0030] The output of summers 105 and 107 form the inputs to speakers 16 and 17, respectively,
to create the sound enhanced image shown in FIGURE 2C.
[0031] Turning now to FIGURE 3A there is shown circuit 30 which is designed to accept four
different sound signal inputs, 11, 12, 13, and 21, where input 21 is a monaural signal
for presentation to the rear two speakers of a five-speaker system. Circuit 30 operates
in situations where all five speakers are present to provide an enhanced full dimensional
sound output image to listener 100 via left speaker 16, right speaker 17, center speaker
31, rear left speaker 32, and rear right speaker 33. FIGURE 3B illustrates the sound
images which are produced by prior art systems in which there are five input sound
signals in which the input to the rear speakers is monaural. FIGURE 3C shows sound
images 320 and 321 perceived by listener 100 when the sound input signals are processed
by circuit 30.
[0032] As shown in FIGURE 3A left and right front inputs 11 and 12 are provided as respective
inputs to QX filter 101. As discussed above, this QX filter can be either that shown
in FIGURE 8A or in FIGURE 8B. The left and right outputs of filter 101 then form the
input to the front left and right speakers 16 and 17 in a five-speaker system.
[0033] Center input 13 goes directly to center speaker 31 without modification.
[0034] Expansion circuit 201 receives a monaural sound signal 21, which can come from various
sources such as, by way of example, from the rear "surround" outputs of the above-mentioned
Dolby ProLogic sound system. Circuit 201 operates to convert that monaural input to
an expanded sound image by using the circuit shown in FIGURE 5 or preferably the circuit
shown in FIGURE 6. The output of circuit 201 forms the inputs to left rear and right
rear speakers 32 and 33 to create the sound enhanced image shown in FIGURE 3C.
[0035] Turning now to FIGURE 4A, there is shown circuit 40 which is designed to accept five
different sound signal inputs, 11, 12, 13, 14 and 15, where inputs 14 and 15 are full
stereo inputs for presentation to the rear two speakers 32 and 33 of a five-speaker
system. Circuit 40 operates in situations where all five speakers are present to provide
an enhanced full dimensional sound output image to listener 100 via left speaker 16,
right speaker 17, center speaker 31, left rear speaker 32 and right rear speaker 33.
FIGURE 4B illustrates the sound images which are produced by prior art systems in
which there are five input sound signals in which the input to the rear speakers is
monaural. FIGURE 4C shows sound images 420 and 421 perceived by listener 100 when
the sound input signals are processed by circuit 40.
[0036] As shown in FIGURE 4A, left and right front inputs 11 and 12 are provided as respective
inputs to QX filter 101. As discussed above, this QX filter can be either that shown
in FIGURE 8A or in FIGURE 8B. The left and right outputs of filter 101 then form the
input to the front left and right speakers 16 and 17, respectively, in a five-speaker
system.
[0037] Center input 13 goes directly to center speaker 31 without modification.
[0038] Expansion circuit 401 receives a stereo input signal 14 and 15, which can come from
various sources such as, by way of example, from the rear speaker signals of the Dolby
AC3 outputs of the above-mentioned Dolby surround sound system. Circuit 401 operates
to enhance the stereo rear speaker input to an expanded sound image by using the circuit
shown in FIGURES 8A or 8B or preferably the circuit shown in FIGURE 6. The circuit
shown in FIGURE 8B can be used as shown or in a modified form with attenuators 1615
and 1619 set to -80dB or greater. This enables the circuit in Figure 8B to operate
more like a pair of Q1 filters such as those used in the circuit in Figure 6. The
outputs of circuit 401 form the inputs to left rear and right rear speakers 32 and
33, respectively, to create the sound enhanced image shown in FIGURE 4C.
[0039] It should be noted that the essential difference between FIGURES 1A, 2A and FIGURES
3A, 4A is the elimination of the summing circuits. The elimination of summing switches
may be effectuated by a switch (not shown), thus permitting a single system to handle
2-, 3-, 4- or 5-speaker configurations. The use of subwoofers and other sound enhancement
transducers is left out for convenience. The concepts discussed herein could work
as well for such components.
[0040] Also note that as used herein, a two-speaker system is a system having right and
left front sound transducers. A three-speaker system includes an additional center
front speaker. A five-speaker system adds rear left and right (either stereo or monaural)
speakers, while one four-speaker system eliminates the front center speaker. A second
four-speaker configuration would have left front, center front, right front and a
monaural surround sound speaker in the rear.
[0041] While the concepts of our invention are discussed in relation to Dolby sound systems
they will work on any type of sound system having different front and rear sound input
signals. One example of such other systems is the sound system for the DVD audio-visual
format. The system can also be used with signals available from different sources
such as from a telephone or computer system working in conjunction with a separate
sound source. In addition, while a five input set of signals has been shown and discussed
the number of input signals is not critical. Also, it is important to note that although
it has been assumed that the front speaker input will be stereo the system will work
with a monaural front speaker input by substituting the mono to expanded stereo process
for the QX filter.
[0042] The invention can be arranged to work with various combinations of "n" input signals
and "x" playback speakers. For example, a single input ("n=1") can be expanded to
stereo ("x=2") or a set of left, center and right input signals ("n=3") can be processed
to produce an expanded stereo sound field for playback over a pair of stereo speakers
("x=2"). Thus, the invention is very flexible since the number of inputs can be greater
than the number of speakers ("n>x"), the number of inputs can be equal to the number
of speakers ("n=x") or the number of inputs can be less than the number of speakers
("n<x").
[0043] Although the present invention and its advantages have been described in detail,
it should be understood that various changes, substitutions and alterations can be
made herein without departing from the scope of the invention as defined by the appended
claims.
1. A system for accepting a set of n input signals for presentation to x speakers, where
x is any number, said system comprising:
means for expanding in pairs certain of the signals for presentation to the x speakers;
means for expanding in pairs others of the input signals for presentation to the x
speakers;
means when x is less than n for summing the expanded signal pairs for presentation
to said x speakers; and
wherein one of said n input signals is a center speaker sound signal, and wherein
said system further includes:
means when x is less than n for summing said center speaker signal with one of said
expanded pairs of input signals prior to said presentation to said x speakers.
2. The invention set forth in claim 1 further comprising means for attenuating said center
sound signal prior to said summing of said center speaker signal.
3. The invention set forth in claim 2, wherein said attenuating is in the range of OdB
to 6dB.
4. The invention set forth in claim 1, wherein at least one of said expanding means includes
a QX filter.
5. The invention set forth in claim 1, wherein at least one of said expanding means includes
an OMNI23D filter.
6. The invention set forth in claim 1, wherein at least one of said expanding means includes
a pair of Q1 filters.
7. The invention set forth in claim 1, wherein the first pair of input signals are for
presentation to the front left and right speakers and wherein the other of said input
pairs are for presentation to left and right rear speakers which are not physically
present.
8. The invention set forth in claim 7, wherein the rear pair of input signals are either
monaural or stereo.
9. The invention as set forth in claim 1, wherein at least one of said expanding means
includes a QX dual filter.
10. The invention as set forth in claim 9, wherein said QX dual filter includes means
for attenuating the signals input to said QX dual filter in the range of -20dB to
-80dB.
1. System zum Akzeptieren bzw. Annehmen eines Satzes von n Eingangssignalen zur Präsentation
bzw. Anlegung bzw. Wiedergabe an x Lautsprechern, wobei x eine beliebige Zahl ist,
wobei das System umfasst:
Mittel zum paarweisen Expandieren bestimmter Signale zur Anlegung an die x Lautsprecher;
Mittel zum paarweisen Expandieren anderer der Eingangssignale zur Anlegung an die
x Lautsprecher;
Mittel, wenn x kleiner als n ist, zum Summieren der expandierten Signalpaare zur Anlegung
an die x Lautsprecher; und
wobei eines der n Eingangssignale ein Ton- bzw. Audiosignal für den Mitte- bzw. Center-Lautsprecher
ist, und wobei das System ferner enthält:
Mittel, wenn x kleiner als n ist, zum Summieren des Center-Lautsprechersignals mit
einem der expandierten Eingangssignalpaare vor der Anlegung an die x Lautsprecher.
2. Erfindung nach Anspruch 1, ferner umfassend Mittel zum Dämpfen bzw. Abschwächen der
Center-Tonsignals vor dem Summieren des Center-Lautsprechersignals.
3. Erfindung nach Anspruch 2, wobei die Dämpfung in dem Bereich von 0 dB bis 6 dB liegt.
4. Erfindung nach Anspruch 1, wobei zumindest eines der Expandierungsmittel einen QX-Filter
enthält.
5. Erfindung nach Anspruch 1, wobei zumindest eines der Expandierungsmittel einen OMNI23D-Filter enthält.
6. Erfindung nach Anspruch 1, wobei zumindest eines der Expandierungsmittel ein Paar
Q1-Filter enthält.
7. Erfindung nach Anspruch 1, wobei das erste Paar Eingangssignale zur Anlegung an die
vorderen Links- und Rechts-Lautsprecher bestimmt sind und wobei die anderen der Eingangspaare
zur Anlegung an hintere Links- und Rechts-Lautsprecher bestimmt sind, die nicht körperlich
vorhanden sind.
8. Erfindung nach Anspruch 7, wobei das hintere Paar Eingangssignale monoaural bzw. monophon
oder stereo ist.
9. Erfindung nach Anspruch 1, wobei zumindest eines der Expandierungsmittel einen QX-Dualfilter
enthält.
10. Erfindung nach Anspruch 9, wobei der QX-Dualfilter Mittel enthält, um die in den QX-Dualfilter
eingegebenen Signale in dem Bereich von -20 dB bis -80 dB zu dämpfen bzw. abzuschwächen.
1. Système pour accepter un ensemble de
n signaux d'entrée pour présentation à
x haut-parleurs,
x étant un nombre quelconque, ledit système comprenant :
des moyens pour expanser par paires certains des signaux pour présentation aux x haut-parleurs,
des moyens pour expanser par paires d'autres des signaux d'entrée pour présentation
aux x haut-parleurs,
des moyens, lorsque x est inférieur à n, pour additionner les paires de signaux expansés pour présentation aux x haut-parleurs,
et
dans lequel l'un desdits n signaux d'entrée est un signal sonore d'un haut-parleur central et dans lequel ledit
système comprend, en outre :
des moyens, lorsque x est inférieur à n, pour additionner ledit signal de haut-parleur central avec l'une desdites paires
expansées de signaux d'entrée avant ladite présentation aux x haut-parleurs.
2. Invention selon la revendication 1, comprenant, en outre, des moyens pour atténuer
ledit signal sonore central avant ladite addition dudit signal de haut-parleur central.
3. Invention selon la revendication 2, dans laquelle ladite atténuation est réalisée
dans la plage de 0 dB à 6 dB.
4. Invention selon la revendication 1, dans laquelle au moins l'un desdits moyens d'expansion
comprend un filtre QX.
5. Invention selon la revendication 1, dans laquelle au moins l'un desdits moyens d'expansion
comprend un filtre OMNI23D.
6. Invention selon la revendication 1, dans laquelle au moins l'un desdits moyens d'expansion
comprend une paire de filtres Q1.
7. Invention selon la revendication 1, dans laquelle la première paire de signaux d'entrée
est prévue pour présentation aux haut-parleurs droit et gauche avant et dans laquelle
l'autre desdites paires d'entrée est prévue pour présentation aux haut-parleurs droit
et gauche arrière, qui ne sont pas physiquement présents.
8. Invention selon la revendication 7, dans laquelle la paire arrière de signaux d'entrée
est constituée de signaux monauraux ou stéréo.
9. Invention selon la revendication 1, dans laquelle au moins l'un desdits moyens d'expansion
comprend un filtre double QX.
10. Invention selon la revendication 9, dans laquelle ledit filtre double QX comprend
des moyens pour atténuer l'entrée de signaux vers ledit filtre double QX dans la plage
de -20dB à -80dB.